Test method development and determination of three-dimensional stiffness properties of polyvinyl chloride structural foams

A study has been conducted to develop proper test methods and to utilize the tests to evaluate three-dimensional mechanical behavior of a polyvinyl chloride structural foam (Divinycell H80 with nominal density of 80kg/m(3)). Transversely isotropic foam microstructure was examined and it revealed that the cell size aspect ratio in in-plane directions was near unity but greater than one in the out-of-plane (rise) direction. Foam stiffness properties, i.e. moduli and Poisson's ratios, were obtained in different loading modes, along both in-plane and out-of-plane directions. The influence of test specimen geometry on compressive properties was studied. Foam specimens with both straight-side and reduced gage sections were designed, fabricated and tested. The effect of specimen gage-section aspect ratio was identified as a critical geometric parameter, affecting foam compressive properties. For foam tensile properties, specimens with different cross-sectional dimensions in the gage section were used. The results revealed transversely isotropic characteristics of the foam material. To evaluate foam shear properties a scaled shear test method was developed. The results indicated a significant difference in in-plane and out-of-plane foam shear stiffness properties.